Thermal power generation is one of the primary sources of electricity worldwide, and the key to improving power generation efficiency lies in developing more efficient ultra-supercritical (USC) power plants. This requires developing new heat-resistant steels capable of withstanding higher temperatures and pressures. G115 steel is a promising candidate material, but its long-term creep strength still needs improvement. Professor Lian-Yong Xu's team at Tianjin University reveal the microstructural evolution of G115 steel during high-temperature creep and provide new insights into enhancing its long-term creep strength.
Highlights
Cu-rich phase strengthening mechanism: G115 steel precipitates Cu-rich phases (CuRP) during creep. These CuRP effectively hinder dislocation motion, thereby improving the material's short-term creep strength.
The key role of stress/strain: Explained the influence of stress/strain on CuRP precipitation and coarsening, as well as the segregation behavior of solute atoms around dislocations, providing key information for understanding the creep mechanism of G115 steel.
CuRP nucleation mechanism: Revealed the unique nucleation mechanism of CuRP in G115 steel during creep and found that manganese can promote CuRP nucleation.
Fig. 1. Microstructural evolution of G115 steel during long-term creep at 650 °C and 140 MPa. (a) After 100 h; (b) after 302 h; (c) after 1045 h; (d) after 2000 h; (e) after 2945 h; (f) after 4132 h (ruptured sample); A magnified area is indicated in the bottom left of each map, and there are four types of precipitates containing CuRP, M23C6, MX, and Laves phase particles during creep process.
Fig. 2. Microstructure of G115 steel after creep for 2000 h at 650 °C and 140 MPa. (a) Irregular Laves-phase particles with SAED along [1-21-3] zone axis; (b) A magnified HAADF STEM image showing ellipsoidal CuRP with SAED along [-112] zone axis; and (c) EDS X-ray maps of the selected areas for alloying elements of Si, Cr, Cu, Fe, Nb, and W.
Fig. 3. (a) Atom images of elements by isoconcentration surfaces at 0.8 at.% Cu in G115 steel after 2000 h creep at 650 °C and 140 MPa (black arrows indicate dislocations); and (b) Magnified atom maps of Cu, Cr, V, Nb, Mn, B, and N near the dislocations.
Authors
The first author of this work is Bo Xiao from Tianjin University, and Professor Lian-Yong Xu from Tianjin University is the corresponding author of this paper.
B. Xiao, L. Xu, C. Cayron, J. Xue, G. Sha, R. Logé, Solute-dislocation interactions and creep-enhanced Cu precipitation in a novel ferritic-martensitic steel, Acta Materialia 195 (2020) 199-208. DOI: https://doi.org/10.1016/j.actamat.2020.05.054
Editor: Dr. Jun-Jing He
